libutil/args: warn on unknown settings after parsing all flags

Upstream change: https://github.com/NixOS/nix/pull/10701

Change-Id: Icf271df57ec529dd8c64667d1ef9f6dbf02d33d3

doc/manual/change-authors.yml

@@ -36,6 +36,10 @@ artemist:
   display_name: Artemis Tosini
   forgejo: artemist
 
+cole-h:
+  display_name: Cole Helbling
+  github: cole-h
+
 edolstra:
   display_name: Eelco Dolstra
   github: edolstra

doc/manual/rl-next/fix-silent-unknown-options.md

@@ -0,0 +1,30 @@
+---
+synopsis: Warn on unknown settings anywhere in the command line
+prs: 10701
+credits: [cole-h]
+category: Improvements
+---
+
+All `nix` commands will now properly warn when an unknown option is specified anywhere in the command line.
+
+Before:
+
+```console
+$ nix-instantiate --option foobar baz --expr '{}'
+warning: unknown setting 'foobar'
+$ nix-instantiate '{}' --option foobar baz --expr
+$ nix eval --expr '{}' --option foobar baz
+{ }
+```
+
+After:
+
+```console
+$ nix-instantiate --option foobar baz --expr '{}'
+warning: unknown setting 'foobar'
+$ nix-instantiate '{}' --option foobar baz --expr
+warning: unknown setting 'foobar'
+$ nix eval --expr '{}' --option foobar baz
+warning: unknown setting 'foobar'
+{ }
+```

src/libutil/args.cc

@@ -93,7 +93,6 @@ void RootArgs::parseCmdline(const Strings & _cmdline)
         verbosity = lvlError;
     }
 
-    bool argsSeen = false;
     for (auto pos = cmdline.begin(); pos != cmdline.end(); ) {
 
         auto arg = *pos;
@@ -122,10 +121,6 @@ void RootArgs::parseCmdline(const Strings & _cmdline)
                 throw UsageError("unrecognised flag '%1%'", arg);
         }
         else {
-            if (!argsSeen) {
-                argsSeen = true;
-                initialFlagsProcessed();
-            }
             pos = rewriteArgs(cmdline, pos);
             pendingArgs.push_back(*pos++);
             if (processArgs(pendingArgs, false))
@@ -135,8 +130,7 @@ void RootArgs::parseCmdline(const Strings & _cmdline)
 
     processArgs(pendingArgs, true);
 
-    if (!argsSeen)
+    initialFlagsProcessed();
-        initialFlagsProcessed();
 
     /* Now that we are done parsing, make sure that any experimental
      * feature required by the flags is enabled */

tests/functional/eval.sh

@@ -51,3 +51,7 @@ mkdir -p $TEST_ROOT/xyzzy $TEST_ROOT/foo
 ln -sfn ../xyzzy $TEST_ROOT/foo/bar
 printf 123 > $TEST_ROOT/xyzzy/default.nix
 [[ $(nix eval --impure --expr "import $TEST_ROOT/foo/bar") = 123 ]]
+
+# Test that unknown settings are warned about
+out="$(expectStderr 0 nix eval --option foobar baz --expr '""' --raw)"
+[[ "$(echo "$out" | grep foobar | wc -l)" = 1 ]]

tests/functional/misc.sh

@@ -30,3 +30,12 @@ expectStderr 1 nix-instantiate --eval -E '[]' -A 'x' | grepQuiet "should be a se
 expectStderr 1 nix-instantiate --eval -E '{}' -A '1' | grepQuiet "should be a list"
 expectStderr 1 nix-instantiate --eval -E '{}' -A '.' | grepQuiet "empty attribute name"
 expectStderr 1 nix-instantiate --eval -E '[]' -A '1' | grepQuiet "out of range"
+
+# Unknown setting warning
+# NOTE(cole-h): behavior is different depending on the order, which is why we test an unknown option
+# before and after the `'{}'`!
+out="$(expectStderr 0 nix-instantiate --option foobar baz --expr '{}')"
+[[ "$(echo "$out" | grep foobar | wc -l)" = 1 ]]
+
+out="$(expectStderr 0 nix-instantiate '{}' --option foobar baz --expr )"
+[[ "$(echo "$out" | grep foobar | wc -l)" = 1 ]]